About a year ago my homebuilt PC started hanging seemingly at random, especially whenever on the "Steam" UI. My GPU was old and overheating, so i upgraded (a little ) to a geforce 8800gt and new PSU. This didnt fix it, but the hangs became less frequent. It has recently gotten a lot worse, hanging in internet browsers and "alt+tab"ing. I have reinstalled windows on different hard drives, changed RAM, and updated all my drivers to no avail.
The only thing left to my mind is to change my CPU and Motherboard...so before i do that, is there anything obvious that ive forgotten to check? (i was thinking of a AMD Phenom II X4 940 CPU and Asus M3A32-MVP Motherboard btw)
Please reply even if you cant think of any other solution, as at least ill know I'm on the right lines.
First thing I would guess is the RAM voltage -- regardless of whether you have new RAM or old RAM, if it's not getting as much power as it's supposed to, it'll cause system freezes. If that is indeed the problem, it's pretty simple to fix. So post your RAM specs and that should be easy to figure it out. It's probably one of the most common causes of a randomly freezing system.
One other possibility is a conflict between active programs and some other program that tries to start running a task in the background. That can lock up the system, or at least kick you out of a game, if they're trying to use the same resource.
This used to happen to me all the time when I would be in certain games and my antivirus program (Panda, at the time) tried to update itself and open a little pop-up balloon. Snoozing the AV program would let me play with no interruptions. Eventually, with a different AV program, the problem stopped happening entirely.
If so, then it looks like it takes 1.8V, which is the standard amount for DDR2. Your motherboard should be providing the correct voltage by default, unless it's retarded. So I am thinking it's less likely that voltage is the problem.
Unless you have all four DIMM slots filled with memory -- that can sometimes cause the memory to require more voltage than the listed specs. But if not, the memory should be working fine.
If you still get the freezes, I'd try downloading memtest86+ and running it for several passes to see if it finds any physical errors in the RAM. That can also cause freezes and crashes. If it comes out clean, I'd go back to looking at software issues.